The present invention relates generally to an integrated circuit (xe2x80x9cICxe2x80x9d). More specifically, this invention relates to the fabrication of an integrated circuit having an improved method and apparatus for an increased throughput furnace nitride bottom anti-reflective coating (xe2x80x9cBARCxe2x80x9d) process.
The present invention applies particularly to the fabrication of logic devices and integrated circuits. Some examples of integrated circuits include an EPROM, an EEPROM, a flash memory device, and a complementary metal oxide silicon (xe2x80x9cCMOSxe2x80x9d) type device. An exemplary device may comprise a field-effect transistor (xe2x80x9cFETxe2x80x9d) containing a metal gate over thermal oxide over silicon (xe2x80x9cMOSFETxe2x80x9d), as well as other ultra-large-scale integrated-circuit (xe2x80x9cULSIxe2x80x9d) systems.
Integrated circuits are utilized in a wide variety of commercial and military electronic devices, including, e.g., hand held telephones, radios and digital cameras. The market for these electronic devices continues to demand devices with a lower voltage, a lower power consumption and a decreased chip size. Also, the demand for greater functionality is driving the xe2x80x9cdesign rulexe2x80x9d lower, for example, into the sub-half micron range. The sub-half micron range may comprise, e.g., decreasing from a 0.35-0.25 micron technology to a 0.18 micron or a 0.15 micron technology, or even lower.
In fabricating a conventional circuit cell, polysilicon is preferably used for a conductive layer formation. The conductive layer is utilized to form a gate structure. In defining a conventional gate structure, polysilicon is first deposited upon a substrate. Next, a BARC layer is formed over the polysilicon. Then a photoresist layer is spun onto the BARC layer.
In order to form the conventional BARC layer, an Si-rich Nitride process is utilized to deposit the BARC layer in a furnace environment. However, for the conventional BARC process, a full furnace load cannot be utilized due to a process variation from the top to the bottom of the furnace deposition device. Thus, an inefficiency is caused in the production of semiconductor devices, because the full physical capacity of the furnace deposition devices cannot be utilized.
For example, in a conventional furnace deposition, a pressure of 100-600 mTorr is utilized. A conventional gas flow comprises ammonia (xe2x80x9cNH3xe2x80x9d) at a flow rate of 10-30 SCCM and Dichlorosilane (xe2x80x9cDCSxe2x80x9d) (SiH2Cl2) at 300-450 SCCM. Conventionally, the furnace deposition experiences a temperature in a first or top zone of 750-770xc2x0 C., a second or center zone temperature of 720-730xc2x0 C., and a third or bottom zone of 700-720xc2x0 C. Conventionally, the top, center and bottom zones comprise approximately equal volumetric divisions of the furnace deposition device.
Because of the relatively low concentrations of NH3 utilized in the conventional BARC layer furnace deposition process, it is relatively difficult to obtain a uniform quality of the semiconductor devices if the entire furnace device is loaded, i.e., if the entire volume available is utilized or filled with a complete load of semiconductor devices, or wafers, to be coated with a BARC layer.
For example, if the device is utilized at a full load rate, then the thickness, the refractive index (xe2x80x9cRIxe2x80x9d), the extinction coefficient (xe2x80x9ckxe2x80x9d) and the reflectivity are degraded. Also, the temperature gradient across the furnace deposition device causes problems with the uniformity of these factors and thus causes problems with uniformity of the deposition of the BARC layer across all of the full load of wafers. Thus, a reduced load is run in the device so as to avoid the extremes of temperature, e.g., in the upper portions of the top zone and lower portion of the bottom zone. This reduced load, in turn, allows for a more uniform deposition of the BARC layer.
One solution conventionally practiced is to utilize a high, i.e., an excessive, flow rate of DCS in order to attempt to maintain load uniformity. However, utilizing these excessive DCS flow rates may cause, for example, a buildup of more byproducts on the exhaust components. Thus, not only is a full load not presently able to be utilized within the furnace deposition devices, but when nearly a full load is utilized with excessive flow rates of DCS, the maintenance requirements of the exhaust components becomes a problem. Also, with excessive DCS, an increased problem with particulates is encountered.
What is needed is a device and method for improving the throughput of a BARC layer furnace deposition device. What is also needed is a device and method for improving the ability of the BARC layer furnace deposition device to operate with a relatively reduced DCS flow. What is also needed is a device and method for improving the ability of the BARC layer furnace deposition device to operate with a reduced temperature gradient across the furnace device. What is also needed is a device and method for improving the maintenance and/or reducing the exhaust components and/or reducing the particulates of a BARC layer furnace deposition device.
Embodiments of the present invention are best understood by examining the detailed description and the appended claims with reference to the drawings. However, a brief summary of embodiments of the present invention follows.
Briefly described, an embodiment of the present invention comprises a device and a method that provides for an improved throughput of a BARC layer furnace deposition device. This improvement is achieved by providing for a higher flow rate of NH3 during the BARC deposition process. Also, this improvement may be achieved by reducing the temperature gradient of the BARC layer furnace deposition device to approximately 715-750xc2x0 C.
For example, NH3 diluted in at least one of Argon, Nitrogen, and Helium, e.g., approximately a 1-10% blend of NH3 in Ar, may be utilized. By diluting the NH3, a higher flow rate may be utilized in the furnace deposition device, thus allowing for an increased load, and uniformity of the BARC layer thickness, refractive index, extinction coefficient, and reflectivity characteristics.
Also, the NH3 depletion is reduced and preferably eliminated due to the higher flow rate of the diluted NH3. Further, this diluted NH3 allows for a reduced DCS requirement, thus reducing maintenance requirements, exhaust component contamination, and also allows for a lowering of the particulates. The diluted NH3 is preferably supplied at approximately 200-500 SCCM, and the DCS flow rate is preferably reduced to approximately 100-150 SCCM, at a pressure of approximately 100-600 mTorr and may also be supplied within a more narrow range of 200-350 mTorr.
Other arrangements and modifications will be understood by examining the detailed description and the appended claims with reference to the drawings.